The majority of the African slave trade consisted of Europeans trading African tribes for slaves. The slave trade became so lucrative for Africans themselves that they frequently waged war against other tribes in an attempt to secure captives for the trade. Among those kingdoms who profited from the slave trade was the kingdom of Ndongo, which Portuguese traders referred to as Angola, after the title of the Ndongo King. Portuguese slaving efforts were opposed by a powerful Queen, Nzinga, who dressed as a man and insisted her subjects refer to her as the King. On one occasion, when she met with the Portuguese governor of Angola and he refused to offer her a chair, she sat on the back of her servant while she negotiated with him.
The main thing that the slave trade did to African political structures was to give more power to those nations or kingdoms that were in position to profit from the trade.
In Africa, most of the slaves did not come from coastal areas. Instead, the slaves came from inland. They were captured and sold by the coastal people to the Europeans. This made the coastal nations much more powerful. By selling slaves to the Europeans, these nations got access to such things as trade goods and guns. These things gave them much more economic and military power and allowed them to become more politically dominant.